Machine for sorting paper stacks



Aug. 1 1967 c;' E. BORCHERT ETAL 3,335,859

MACHINE FOR SORTING PAPER STACKS 2 Sheets-Sheet 1 Filed Sept. 21, 1965 15, 1967 G- E. BORCHERT ETAL 3,335,859

MACHINE FOR SORTING PAPER STACKS Filed Sept. 21, 1965 2 Sheets-Sheet 2 United States Patent Pingel, Berlin, Germany, assignors to Bundesdruckerei, Berlin, Germany Filed Sept. 21, 1965, Ser. No. 488,982 Claims priority, application Germany, Sept. 21, 1964,

n 3 Claims. (Cl. 209--111.6)

The invention relates to a machine for sorting paper stacks, normally alternatively, but in exceptional cases also for irregularly stacked printed and interleaving sheets of the same sizes.

There are already known devices for lifting and transporting the uppermost sheet of a stack by means of two pneumatic lifting devices arranged on opposite sides of the stack which remove the sheet at choice towards different sides.

With steel plate photogravure printing, newly printed sheets should not be stacked on top of each other, because the inks have not fully dried when the sheets are laid off. It is therefore necessary to interleave special sheets of blotting paper in order to prevent transfer of the ink to the next sheet. This interleaving is effected automatically on the printing presses.

When the ink has reliably dried after a certain period, these interleaves must again be removed from the stack. Hitherto, this could be effected only by hand because known devices were incapable of meeting this requirement. Owing to the strong application required for steel plate photogravure printing, the interleaving sheets tend to adhere to the printed sheets. This is a further reason, why the extraction and sorting cannot be effected by machines.

The present invention has the object of rendering devices of known construction, such as so-called feeders, suitable for sorting sheets.

According to the invention, this object may be realized in that the pneumatic lifting devices are associated with light sources and photoelectric cells which control the operation of the sheet lifting devices as a function of the differential brightness values of the sheet surfaces.

However, the proper operation of the device according to the invention is guaranteed only if the stack or the topmost sheet at the time and the brightness value of which is to be detected by the photoelectric cells, are always moved into the same distance from these photoelectric cells.

For this reason, as already known from stack elevators for pneumatic sheet feeders, there are provided several independently operating and individually controlled chain elevators.

The invention will be further explained, by way of example, with reference to the accompanying drawing, in which:

FIG. 1 is a side elevation of the paper stack sorting machine according to the invention;

FIG. 2 is a top view of the machine of FIG. 1.

The paper stack sorting machine consists substantially of two identical feeder attachments which are so connected to one unit that their forwarding sides are oppositely directed. A stack elevator is provided in the centre of the machine.

The paper stack to be sorted is shown at 1 and is fitted into the centre of the machine by means of a lateral stack feeder, not shown, and is lifted by means of the stack elevator 2, 3 until the topmost sheet is adjacent to the pneumatic lifting devices 4 and 5. The surface of the sheet is scanned by photoelectric cells 6 and 7 and the suction air of one of the lifting devices is controlled according to whether the topmost sheet is a printed or interleaving sheet. The mechanically alternating control of the devices would not be satisfactory since, with frequent use of the interleaving sheets, several of these are frequently deposited by the printing press between the printed sheets at the same time. Since these interleaving sheets tend to adhere easily to the printed sheets and the type of paper is permeable to the suction air, it is necessary to prevent a printed sheet from being lifted at the same time. This is achieved by means of two springs 8 which engage into lateral recesses of the interleaving sheet on the side towards which the same is pulled off. These springs 8 retain the printed sheet under the interleaving sheet during the removal of the latter.

The stack 1, comprising about 1000 printed and interleaving sheets each is not flat, owing to the fact that the paper is stretched during photogravure printing and the gripper edge has not been stretched. In order to move the upper edges of both sides uniformly to the pneumatic lifting devices 4 and 5, the stack sorting machine is equipped with a stack elevator, consisting of two independently operated chain elevators 2 and 3, each driven by a motor. Each motor is controlled by a scanner 9 and 10, respectively, so that the level gaps between the stack edges and the suction rods can be accurately observed. This is important for the good functioning of the photoelectric cells because these can scan the surface accurately only within a limited height range in order to control the suction air.

What we claim is:

1. A device for lifting and removing the topmost sheet from a stack of sheets by means of two pneumatic lifting devices arranged on opposite sides of the stack which remove the selected sheet towards different sides, characterized in that for sorting different sheets, these pneumatic lifting devices are associated with light sources and photoelectric cells which control the operation of the lifting devices as a function of the differential brightness values of the surfaces of the sheets.

2. A device as claimed in claim 1, characterized in that the stack elevator is moved by two independently driven chain elevators, which are individually controlled by scanners.

3. A device as claimed in claim 1, characterized in that springs are provided on one side of one of the two lifting devices for retaining the sheet under the sheet to be detached and engaging through recesses in the sheet to be detached.

References Cited UNITED STATES PATENTS 2,626,147 l/l953 Gjostein 271-26 X 3,069,013 12/1962 Neubrech et al. 20911l.6 3,146,902 9/1964 Voelker 271-30 X 3,197,647 7/1965 Fraenkel 20911l.7 X 3,294,396 12/1966 Staines 27126 M. HENSON WOOD, In, Primary Examiner. J. N. ERLICH, Assistant Examiner. 

1. A DEVICE FOR LIFTING AND REMOVING THE TOPMOST SHEET FROM A STACK OF SHEETS BY MEANS OF TWO PNEUMATIC LIFTING DEVICES ARRANGED ON OPPOSITE SIDES OF THE STACK WHICH REMOVE THE SELECTED SHEET TOWARDS DIFFERENT SIDES, CHARACTERIZED IN THAT FOR SORTING DIFFERENT SHEETS, THESE PNEUMATIC LIFTING DEVICES ARE ASSOCIATED WITH LIGHT SOURCES AND PHOTOELECTRIC CELLS WHICH CONTROL THE OPERATION OF THE LIFTING DEVICES AS A FUNCTION OF THE DIFFERENTIAL BRIGHTNESS VALUES OF THE SURFACES OF THE SHEETS. 